Sayana

Sayana's main claim to fame is that he supposedly wrote a commentary1 on the Rig-Veda, the classic English edition of which was translated by Max Müller in the mid-19th century.

Among the more curious details about this commentary is the fact that some modern scholars seem convinced that, in it, Sayana demonstrated a near-accurate calculation of the speed of light:

"O Sun! You see all, create brightness and travel very fast. You brighten the whole sky." (Rig-veda 1:50:4)Sayana comments:
"It is remembered that Sun traverses 2,202 yojanas in half a nimesa."

With some calculation, this figure (conjecturally using the Sun as a symbol of light) converts to c. 299,000 km/s, very close to the established value for the speed of light.2

Notes:

1 I say "supposedly", because it is generally accepted that, while Sayana probably wrote some of the core commentaries attributed to him, the greater part were written by later commentators, using his name.By convention, however, most scholars use the name "Sayana" to refer collectively to the authors of these commentaries.